Average NorthWestern Energy residential electric customers will pay 24 cents more in their monthly bills starting Jan. 1, while the utility's typical natural gas customers will see a $1.46 drop.
Utility officials said Thursday they are implementing these interim rate adjustments in response to changes in state and local property taxes.
The interim changes must be approved by the Montana Public Service Commission to become permanent. The utility submitted its property tax tracker filing to the Public Service Commission last week.
For the first time, this filing includes an Invasive Species Fee, approved by the 2019 Montana Legislature and assessed on hydro-electric dam operators. NorthWestern customers will pay $921,632 for those fees.
NorthWestern's transmission and distribution arm has the largest property tax value in the state, and its generation division is the third largest, according to the utility.
Customers should expect another rate change in March, although NorthWestern officials say it's too early to say whether rates will rise or fall or by how much.
NorthWestern filed for its first electric general rate review in 2018, and the Public Service Commission approved on Dec. 20 a new rate agreement reflecting a $6.5 million cost increase for the utility.
The utility imposed an interim rate increase in the spring to help defray those costs.